My boyfriend says he's a longer... What does he mean?!

Me and this guy have been sleeping together but we have liked each other for 6 years. He keeps telling me that he's a loner by nature and that he doesn't want to hurt me. His actions say differntly he has been fighting in Iraq and was home for 2 weeks and that is when all this stuff came out. What do you think? Why does he keep saying he's a loner by nature what does that mean?